Bottom Line:
Repigmentation of vitiligo depends on available melanocytes from three possible sources: from the hair follicle unit which is the main provider of pigment cells, from the border of vitiligo lesions, and from unaffected melanocytes within depigmented areas; pigment cells at these locations originate a perifollicular, border spreading and a diffuse repigmentation pattern.Melanocyte tissue stem cells located in the niche at the bulge region of the hair follicle are the most important sources for providing immature pigment cells that undergo terminal differentiation and originate repigmentation, but cytokines, UVR and other molecules acting in melanogenesis with adequate regulation mechanisms contribute to successful recovery in vitiligo.The presence of keratinocyte stem cells in the interfollicular epidermis raises the question on the possibility of melanocyte stem cells in a similar location and the development of future strategies for therapeutic purposes.

ABSTRACTRepigmentation of vitiligo depends on available melanocytes from three possible sources: from the hair follicle unit which is the main provider of pigment cells, from the border of vitiligo lesions, and from unaffected melanocytes within depigmented areas; pigment cells at these locations originate a perifollicular, border spreading and a diffuse repigmentation pattern. In order for repigmentation to take place under stimulation with diverse therapies, melanocytes should be present in appropriate numbers. Melanocyte tissue stem cells located in the niche at the bulge region of the hair follicle are the most important sources for providing immature pigment cells that undergo terminal differentiation and originate repigmentation, but cytokines, UVR and other molecules acting in melanogenesis with adequate regulation mechanisms contribute to successful recovery in vitiligo. The presence of keratinocyte stem cells in the interfollicular epidermis raises the question on the possibility of melanocyte stem cells in a similar location and the development of future strategies for therapeutic purposes.

Figure 0003: Diffuse repigmentation pattern. Several patches of repigmentation on the dorsum of forearm in this patient indicate recovery with a diffuse pattern

Mentions:
Although the concept of melanocyte reservoir is mostly used to designate the hair follicle unit, melanocytes for repigmentation by medical methods arise from three main sources: (a) the hair follicle unit; (b) unaffected melanocytes within areas of depigmented epidermis, and (c) melanocytes located at the edge of vitiligo lesions.[3] When studying the patterns of repigmentation in 125 patients with 352 vitiligo patches treated with different methods, the following repigmentation patterns were observed: (1) perifollicular when treated with systemic and topical PUVA [Figure 1]; (2) marginal, after systemic PUVA and topical calcipotriol [Figures 2 and 3] diffuse, when on topical steroids [Figure 3].[4] Nevertheless, most melanocytes originate from the hair follicle unit where they are present in large numbers and migrate towards the epidermis. A striking feature of the hair follicle reservoir is the enormous potential for providing pigment cells considering its minute size and diameter.

Figure 0003: Diffuse repigmentation pattern. Several patches of repigmentation on the dorsum of forearm in this patient indicate recovery with a diffuse pattern

Mentions:
Although the concept of melanocyte reservoir is mostly used to designate the hair follicle unit, melanocytes for repigmentation by medical methods arise from three main sources: (a) the hair follicle unit; (b) unaffected melanocytes within areas of depigmented epidermis, and (c) melanocytes located at the edge of vitiligo lesions.[3] When studying the patterns of repigmentation in 125 patients with 352 vitiligo patches treated with different methods, the following repigmentation patterns were observed: (1) perifollicular when treated with systemic and topical PUVA [Figure 1]; (2) marginal, after systemic PUVA and topical calcipotriol [Figures 2 and 3] diffuse, when on topical steroids [Figure 3].[4] Nevertheless, most melanocytes originate from the hair follicle unit where they are present in large numbers and migrate towards the epidermis. A striking feature of the hair follicle reservoir is the enormous potential for providing pigment cells considering its minute size and diameter.

Bottom Line:
Repigmentation of vitiligo depends on available melanocytes from three possible sources: from the hair follicle unit which is the main provider of pigment cells, from the border of vitiligo lesions, and from unaffected melanocytes within depigmented areas; pigment cells at these locations originate a perifollicular, border spreading and a diffuse repigmentation pattern.Melanocyte tissue stem cells located in the niche at the bulge region of the hair follicle are the most important sources for providing immature pigment cells that undergo terminal differentiation and originate repigmentation, but cytokines, UVR and other molecules acting in melanogenesis with adequate regulation mechanisms contribute to successful recovery in vitiligo.The presence of keratinocyte stem cells in the interfollicular epidermis raises the question on the possibility of melanocyte stem cells in a similar location and the development of future strategies for therapeutic purposes.

ABSTRACTRepigmentation of vitiligo depends on available melanocytes from three possible sources: from the hair follicle unit which is the main provider of pigment cells, from the border of vitiligo lesions, and from unaffected melanocytes within depigmented areas; pigment cells at these locations originate a perifollicular, border spreading and a diffuse repigmentation pattern. In order for repigmentation to take place under stimulation with diverse therapies, melanocytes should be present in appropriate numbers. Melanocyte tissue stem cells located in the niche at the bulge region of the hair follicle are the most important sources for providing immature pigment cells that undergo terminal differentiation and originate repigmentation, but cytokines, UVR and other molecules acting in melanogenesis with adequate regulation mechanisms contribute to successful recovery in vitiligo. The presence of keratinocyte stem cells in the interfollicular epidermis raises the question on the possibility of melanocyte stem cells in a similar location and the development of future strategies for therapeutic purposes.